These types of folding bicycles, which are sometimes also known as collabsible bicycles or camping bicycles for example, are known in various types of designs. In order to achieve relatively small external dimensions, a plurality of known examples of such folding bicycles are equipped with relatively small wheels. This means that in most cases the bicycles must be driven in quite high gear which naturally causes problems when riding up inclines. These types of folding bicycles usually had only one massively built frame tube with one hinge, the front end of this frame tube being equipped with an attachment for the shaft tube and the rear end in a frame part for attachment of the saddle bar as well as for mounting the crank of the chain drive.
Furthermore, DE 44 23 647 A1 for example has made known designs of folding bicycles which are equipped with wheels comparable with those of standard street bicycles and as such are accordingly comfortable to ride, and corresponding gear shifts on inclines are possible. Furthermore, an accordingly greater amount of gear rings and gear shifts can be installed on these bicycles. In order to fold such bicycles with comparably large front and back wheels, a complicated turning and locking mechanism is usually provided to achieve a corresponding reduction of the length dimensions of the frame. In the case of the well known design of a bicycle in accordance with DE 44 23 647 A1 having a frame with a locking, horizontal turning hinge, around whose axis the hinged-on frame parts can be turned after opening the lock, the frame parts are slideable by means of a horizonally extendable telescope and/or by means of arms being turnable or pivotable around a vertical axis from that position into a plane parallel to each other, whereby in accordance to this DE-A, as is generally the custom, the aim is to create a bicycle which in an easily manageable way can be stowed in a small space and should be equipped with an optimally rigid frame.
Furthermore, in GB-A 2 287 438 folding bicycles have become known whose wheels each have a different diameter. In this well known variety of a collapsible or folding bicycle the wheels are mounted on conventional forks which embrace the wheels on both sides, making it impossible to completely fold the bicycle it such a way that the wheels are embedded in each other or that one wheel overlaps the other.
Thus the disadvantage of all folding bicycle constructions known so far is the fact that a reduction of the length dimensions of the bicycle as compared to its dimensions in its operating or driving position can be achieved, while at the same time having distinctively greater width dimensions in the folded state, which mainly are a result of the fact that due to the mounting of the front and back wheels in correspondingly wide forks, correspondingly large minimum width dimensions of the bicycle in its folded state cannot be avoided. In order to achieve a certain reduction of thickness in the folded state, it has furthermore already been suggested to at least remove the front wheel from its fork, which of course involves additional work and would require that the front wheel would need to be transported separately in the folded state. In particular the relatively large width of the bicycle also in its folded state due to the mounting of the front and back wheels in forks of course results in problems when transporting the folded bicycle.
In addition to bicycles with foldable frames to reduce the length dimensions of the bicycle as compared to the length dimensions in its operating state, other designs are also known, wherein the height dimensions of the bicycle in its folded state can be reduced by means of correspondingly joining together frame tubes. In these types of constructions, folding together the frame tubes to achieve height reduction naturally results in a reduction of the distance between the front wheel and the back wheel, so that in this case there also arise problems with regards to transporting the bicycle in its folded state, especially with regard to the large total length of the bicycle, even though the width of the bicycle in the case of suitably adjustable handlebars basically is limited to the width of the forks for mounting the front and back wheel as well as the to the crank drive. Naturally only very small wheels can be used for such constructions, which again results in the above-mentioned problems regarding riding comfort and driving characteristics especially with regard to inclines.